How to process images using PHP?

PHP Image Processing Guide provides common functions for creating image resources from JPEG/PNG files, copying/resizing/flipping images. A practical case illustrates how to scale uploaded images into thumbnails. Advanced features include image filters, text watermarks and editing operations (crop/rotate/flip).

The complete guide to processing images with PHP

PHP provides a wide range of functions to process and manipulate images. This guide will familiarize you with all aspects of PHP image processing and make you proficient through practical cases.

Commonly used PHP image processing functions

• imagecreatefromjpeg(): Create image resources from JPEG files.
• imagecreatefrompng(): Create an image resource from a PNG file.
• imagecopy(): Copy part of an image to another image.
• imageresize(): Resize the image.
• imageflip(): Flip the image vertically or horizontally.
• imagesave(): Save image resources as files.

Practical Case

Let’s create a simple script to scale the images uploaded by users into thumbnails:

<?php

if (isset($_FILES['image'])) {
    // 获取上传的文件
    $file = $_FILES['image'];

    // 确保文件合法
    if ($file['error'] !== UPLOAD_ERR_OK) {
        die('上传文件失败');
    }

    // 创建图像资源
    $image = imagecreatefromjpeg($file['tmp_name']);

    // 缩小图像
    $newWidth = 100;
    $newHeight = (int) ($newWidth * (imagesy($image) / imagesx($image)));
    $thumb = imagecreatetruecolor($newWidth, $newHeight);
    imagecopyresized($thumb, $image, 0, 0, 0, 0, $newWidth, $newHeight, imagesx($image), imagesy($image));

    // 保存缩略图
    imagesave($thumb, 'thumbnail.jpg', 90);

    // 显示成功消息
    echo '缩略图已创建';
}

?>

More features

PHP also provides some advanced features such as:

• Image Filters: Apply filters to enhance or modify the appearance of an image.
• Text Watermark: Add watermark to the image.
• Image editing operations: Crop, rotate and flip images.

With these functions and knowledge, you can easily extend your PHP applications to provide users with powerful image processing capabilities.

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